Solid ink jet printers were first offered commercially in the mid-1980's. One of the first such printers was offered by Howtek Inc. and used pellets of colored cyan, yellow, magenta and black ink that were fed into shape coded openings that fed generally vertically into the heater assembly of the printer where they were melted into a liquid state for jetting onto the receiving medium. The pellets were fed generally vertically downwardly, using gravity feed, into the printer. These pellets were elongated and tapered on their ends with separate rounded, five, six, and seven sided shapes each corresponding to a particular color.
Later more successful solid ink printers, such as the Tektronix Phaser.TM., the Tektronix Phaser.TM. 300, and the Jolt printer offered by Dataproducts Corporation, used differently shaped solid ink sticks that were either gravity fed or spring loaded into a feed chute and pressed against a heater plate to melt the solid ink into its liquid form. These ink sticks were shape coded and of a generally small size. One system utilized an ink stick loading system that initially fed the ink sticks into a preload chamber and then loaded the sticks into a load chamber by the action of a transfer lever. Earlier solid or hot melt ink systems used a flexible web of hot melt ink that is incrementally unwound and advanced to a heater location or vibratory delivery of particulate hot melt ink to the melt chamber. None of these systems had effective ways to either identify that an incorrectly colored ink was being loaded for feed to the incorrect color ink reservoir or a simple way to remove such incorrectly fed ink stick from the feed system.
As phase change ink color printers have increased their printing speed the need has developed to provide larger sized ink sticks so that refill of the ink reservoir in the print head is less frequent and more output or prints can be produced between refills. In designs where there is not a steep or generally vertical feed path to the heater plate, some provisions have been made to prevent the solid masses of shaped ink from sticking to the sides of the feed chutes so that an unrestricted feed of ink sticks proceed down into the heater plate for melting and filling of the individual colored ink reservoirs that are usually located within the print head. These larger sized ink sticks are fed into receptacles or openings in a cover plate over the feed chutes. If an ink stick is inadvertently inserted within the wrong receptacle it can be difficult for the printer operator to remove the ink stick, especially because of the sticky nature of the ink sticks' waxy exterior surfaces that can cause them to become wedged in the incorrect ink stick receptacle. If an ink stick is incorrectly oriented within the correct receptacle, it can be difficult for the operator to identify the misorientation and remove the ink stick.
These problems are solved in the design of the present invention by providing a solid ink stick loading system and ink stick design for a plurality of ink stick colors wherein each ink color has a mutually exclusive shape and an ink stick feed cover with a corresponding distinctively shaped opening for each shape that cooperates with the ink sticks such that a correctly colored and shaped ink stick is permitted to drop therethrough into the ink stick feed bin for transmission to the reservoir and an incorrectly colored and shaped ink stick is retained in an elevated position, thereby indicating to the operator that the incorrect color is being fed into the ink stick color chute and facilitating its easy removal by the operator. Each ink stick has a flared portion about the periphery of its opposing sides that permit the ink stick to be retained in a raised position when fed to the incorrect color slot. Additionally, incorrectly oriented ink sticks fed into the correct ink stick receptacle are also retained in a raised position to facilitate identification and removal.